The invention relates to a yarn feeler, such as for a yarn sensor in a yarn feeding device, the yarn feeler having a feeler foot which forms a resting surface which contacts the yarn.
In yarn processing technologies yarn feelers are used which mechanically act on a yarn, e.g., in yarn feeding devices to detect yarn turns which mainly move transversely to their yarn axis. A design has become standard wherein the yarn feeler is bent from a wire section such that its feeler foot forms a substantially U-shaped tongue oriented with its longitudinal axis substantially laterally in relation to the yarn axis so that the yarn to be detected is sweeping along the lower surface of the feeler foot.
From operation and maintenance Manual IWF 9007,9107,9207 of IRO AB,SE, reference number 07 -0939-0812-01/9647, pages 10, 44, 50 and 51, a yarn feeler is known which is designed as a double leg wire bracket and is pivotably held by an axis supported in a housing of a yarn feeding device. The yarn feeler has a feeler foot which is bent downwardly and rests on the yarn turns of a yarn store which wanders forwardly on the storage drum of the yarn feeding device. The yarn feeler can be displaced by the yarn turns out of a home position in order to thereby generate signals for a control or monitoring means. The feeler foot, being U-shaped and having two legs, points in the moving direction of the yarn turns and is inclined obliquely downwardly. During operation of the yarn feeding device contamination and mainly lint is collected in the U-base of the feeler foot until a resulting lint tail is trails from the feeler foot. Said lint collection at the U-base and the lint tail may not only lead to functional disturbances during the yarn detection but also to disturbances downstream of the yarn feelers and to fabric faults if it is torn off and travels further with the yarn. The danger of a disturbance by such collections is particularly high for yarn feelers which permanently rest on yarn turns during normal operation, e.g. as a yarn breakage sensor monitoring presence of the first yarn turns in the yarn supply in a yarn feeding device.
It is a task of the invention to create a yarn feeler of the kind as mentioned above which is characterised by an enhanced operational reliability.
More specifically, the feeler foot of the yarn feeler is provided with an uninterrupted surface at least in the region of its yarn resting surface.
The uninterrupted surface at least in the region of the resting surface of the feeler foot prevents collection of contamination and lint in the feeler foot and suppresses the generation of an undesirable lint tail. In addition the yarnis loaded gently by the contact pressure of the yarn feeler due to the uninterrupted surface in the region of the resting surface, which is expedient in case of delicate yarn qualities and/or high yarn speeds. In this way the overall operational safety of the yarn feeler is enhanced, since disturbances by collections of contaminations in the feeler foot are avoided and since the mechanical load on the yarn being detected is reduced (reduced yarn breakage danger).
The feeler foot can include a shank which is bent upwardly from the main plane of the resting surface, and the uninterrupted surface extends at least into the root of the shank of the feeler foot in order not to offer any possibilities for lint, unavoidably occurring during the yarn processing, to get caught.
The uninterrupted surface has an essentially linear generatrix which is substantially parallel to the yarn axis. Thus, the contact pressure of the feeler foot on the yarn is distributed evenly. The essentially linear generatrice can be made concave, truly straight or convex, depending on the geometrical form of the yarn during detection.
The uninterrupted surface ought to be curved convexly or consist of several surface sections in order to generate a low and constant resistance to the passing yarn and to have the feeler foot properly displaced by the yarn.
The uninterrupted surface should have a part in the tip region of the feeler foot which is essentially parallel to the storage drum periphery. The size of said surface should suffice to cover two adjacent yarn turns simultaneously, particularly in case of yarn separation on the drum.
The uninterrupted surface should be rounded or chamfered in order to exclude edges or cutting regions dangerous for the yarn, particularly when said surface forms the resting surface of the feeler foot.
The feeler foot is a formed part, preferably of metal or plastic, with the uninterrupted surface integrated therewith in a unitary fashion. Said embodiment is advantageous from a manufacturing standpoint. Since the feeler foot should act with only its surface, it even can be made hollow in order to save weight.
The shank is formed by two spaced apart legs which extend to the feeler foot with their outer contours either parallel to each other or converging towards the resting surface. The latter design is particularly important when using the feeler foot in a yarn feeding device, since during threading-up or due to other influences the yarn may temporarily be lifted and hence contact the shank. The converging shank then guides the yarn due to the yarn tension below the resting surface automatically so that entangling of the yarn at the feeler foot or the shank, respectively, can be omitted.
Alternatively, the feeler foot is formed from a wire section, e.g. by bending, and the interspace between its legs is filled by an insert (hollow or solid). The insert so to speak occupies the interspace so that contaminants and lint cannot deposit there.
The feeler foot as bent from wire material is provided with a shoe-like cover which hinders the deposition of contaminants and lint in the interspace between the legs and which also forms the resting surface.
The interspace between the legs of the feeler foot as bent from wire material is covered by a membrane-like plane element which either is set back behind the resting surface or even forms the resting surface, respectively. Also in this case the uninterrupted surface between the legs counteracts to the deposition of contaminants and lint.
The feeler foot is a runner-like plane element defining the resting surface and the uninterrupted surface. It is mounted on the shank such that it is freely ending. This is a particularly lightweight and structurally simple embodiment whereby the deposition of contaminants and lint is avoided.
In the event that a cavity should remain when covering the interspace between the legs of the feeler foot as bent from wire material, said cavity can be occupied by a filling in order to hinder the entrance of contaminants or lint. Said filling could e.g. be foam material or another material (e.g. a potting material) having no other function than the occupation of the cavity.